14. Too fast eating.—Some boys fill their mouths with food. Then they cannot chew their food and cannot mix saliva with it. They swallow their food whole, and then their stomachs have to grind it. The saliva cannot mix with the food and so it is too dry in the stomach. Then their stomachs ache, and they are sick. Eating too fast and too much makes children sick oftener than anything else.
Birds swallow their food whole, for they have no teeth. Instead, a strong gizzard inside grinds the food. We have no gizzards, and so we must grind our food with our teeth.
15. Teeth.—We have two kinds of teeth. The front teeth are sharp and cut the food; the back teeth are flat and rough and grind it. If you bite nuts or other hard things you may break off a little piece of a tooth. Then the tooth may decay and ache.
After you eat, some food will sometimes stick to the teeth. Then it may decay and make your breath smell bad. After each meal always pick the teeth with a wooden toothpick. Your teeth will also get dirty and become stained unless you clean them. Always brush your teeth with water every morning. This will also keep them from decaying.
Digestive organs of a bird.
a esophagus or swallowing tube.
b crop or bag for carrying food.
c stomach.
d intestine.
e gizzard or food grinder.
16. Swallowing.—When food has been chewed and mixed with saliva until it is a paste, it is ready to be swallowed. The tongue pushes the food into a bag just back of the mouth. We call the bag the pharynx. Then the pharynx squeezes it down a long tube and into the stomach. The nose and windpipe also open into this bag, but both are closed by little doors while we swallow. We cannot breathe while we swallow. If the doors are not shut tightly, some food gets into the windpipe and chokes us.
WHAT WE HAVE LEARNED
1. We eat to feed the cells of the body.